Methods and system for detecting fretting

ABSTRACT

Methods and systems are provided for operating a vehicle that includes a piezoelectric device. The piezoelectric device may harvest energy that may be transferred between two masses, such as a chassis and a vehicle suspension, to power electrical components of a vehicle. In addition, output of the piezoelectric device may be monitored to identify degradation of electrical connectors.

FIELD

The present description relates generally to methods and systems formonitoring a system for fretting of electrical connectors. The methodsand systems may be particularly useful for vehicles that areelectrically propelled.

BACKGROUND/SUMMARY

A vehicle may include a battery to provide electrical energy that may beapplied to propel the vehicle. The battery may be comprised of aplurality of battery cells. The battery cells may be connected in serieswith other battery cells to increase battery output voltage. The batterycells may also be connected in parallel with other battery cells toincrease output current capacity of the battery. The battery cells maybe coupled to other battery cells via electrical connections. Theelectrical connections may include two mating surfaces (e.g., a pad anda leg). The two mating surfaces may be soldered together or there may bea friction fit between the two mating surfaces. Vibrations may cause oneof the two mating surfaces to move relative to the other of the twomating surfaces. The relative motion between the two mating surfaces maycause one or both of the mating surfaces to wear and generate an oxidefilm (e.g. fretting). The oxide film may grow and thicken if motionbetween the two mating surfaces continues. The oxide film may increaseand an amount of electrical resistance that is between the two matingsurfaces may increase up to a point where the oxide film forms aninsulator between the two mating surfaces. The connection may no longerbe useful once the two mating surfaces are insulated from each other.Consequently, operation of the battery may degrade.

The inventors herein have recognized the above-mentioned issues and havedeveloped a vehicle operating method, comprising: generating anelectrical output via a piezoelectric device, the piezoelectric devicecoupled to a mount that insulates a first vehicle component from asecond vehicle component; and indicating degradation of an electricalconnector in response to the electrical output.

By monitoring output of a piezoelectric device, it may be possible todetermine vehicle operating conditions that may contribute todegradation of electrical connections in a battery and/or vehicleelectric power system. For example, the piezoelectric device may respondto vibrational signal frequencies and magnitudes that may be indicativeof conditions that may cause degradation of electrical connectors. Inparticular, the piezoelectric device may output a voltage that reflectsthe vibrational signal frequencies and a controller may respond tooutput of the piezoelectric device to determine if degradation ofelectrical connectors may result from the vibrational frequencies. Thepiezoelectric devices may also operate to harvest mechanical energybetween two masses and convert the harvested mechanical energy intoelectrical energy. The electrical energy may be used to propel thevehicle and power ancillary electrical devices.

The present description may provide several advantages. In particular,the approach may allow degradation of electrical connections to bepredicted. Further, the approach generates electric power whiledetermining whether or not vibrational energy may affect degradation ofelectrical connectors. In addition, the approach may provide mitigatingactions when undesirable vibrations occur in a vehicle system.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a vehicle driveline;

FIG. 2 is a cut-away view of a vibration insulating mount that includespiezoelectric devices;

FIG. 3 is a plot that shows vibrational energy that may influencefretting of electrical connections;

FIG. 4 is a plot that shows a relationship between excitation level andrate of resistance change for electrical connectors;

FIG. 5 is a vehicle operating sequence where output of a piezoelectricdevice is a basis for indicating fretting of electrical connectors;

FIG. 6 is a flowchart of a method for delivering electrical power andpredicting fretting of electrical connections via a piezoelectricdevice; and

FIGS. 7A and 7B show an example electrical connection between twoelectrical devices.

DETAILED DESCRIPTION

The following description relates to systems and methods for operating avehicle that includes one or more piezoelectric devices. FIG. 1 shows anexample vehicle system that includes a driveline with one or moreelectrical propulsion sources. The electrical propulsion sources may beoperated with electrical energy that is generated via the one or morepiezoelectric devices. A detailed view of a mounting device thatincludes piezoelectric devices is shown in FIG. 2 . The mounting devicemay provide insulation from vibrations transferred from a first mass toa second mass. FIG. 3 shows example output characteristics forpiezoelectric devices for a vehicle at different mileage levels. FIG. 4shows a relationship between an excitation level of an electricalconnection and a rate of resistance change for the electricalconnection. An example vehicle operating sequence according to thepresent invention is shown in FIG. 5 . A method for operating a vehiclethat includes piezoelectric devices is shown in FIG. 6 . An exampleelectrical connection between two electrical devices is shown in FIGS.7A and 7B.

FIG. 1 illustrates an example vehicle propulsion system 100 for vehicle121. Throughout the description of FIG. 1 , mechanical connectionsbetween various components are illustrated as solid lines, whereaselectrical connections between various components are illustrated asdashed lines. Vehicle propulsion system 100 is shown with a firstelectric machine (e.g., a propulsive force electric machine) 120 and asecond electric machine (e.g., a propulsive force electric machine) 135for propelling vehicle 121. However, in other examples, vehicle 121 mayinclude only one electrical machine for providing propulsive force.Electric machine 120 and electric machine 135 are controlled viacontroller 12. The controller 12 receives signals from the varioussensors shown in FIG. 1 . In addition, controller 12 employs theactuators shown in FIG. 1 to adjust driveline operation based on thereceived signals and instructions stored in memory of controller 12. Insome examples, the vehicle propulsion system 100 may include an internalcombustion engine (not shown). Controller 12 includes a centralprocessor 23, read only (non-transitory) memory 24, random access memory25, and inputs and outputs 26.

Vehicle propulsion system 100 has a front axle 133 and a rear axle 122.In some examples, rear axle may comprise two half shafts, for examplefirst half shaft 122 a, and second half shaft 122 b. Vehicle propulsionsystem 100 further includes front wheels 130 and rear wheels 131. Inthis example, front wheels 130 and/or rear wheels 131 may be driven viaelectrical propulsion sources. The rear axle 122 is coupled to electricmachine 120. Electric machine 120 is shown incorporated into axle 122and electric machine 135 is shown incorporated into front axle 133. Rearaxle 122 may include a transmission or gearbox 120 a that shifts from afirst gear to a second gear or vice-versa. Likewise, front axle 133 mayinclude a transmission or gearbox 135 a that shifts from a first gear toa second gear or vice-versa.

Electric machines 120 and 135 may receive electrical power from onboardelectrical energy storage device 132. Furthermore, electric machines 120and 135 may provide a generator function to convert the vehicle'skinetic energy into electrical energy, where the electrical energy maybe stored at electric energy storage device 132 for later use by theelectric machine 120 and/or 135. A first inverter system controller(ISC1) 134 may convert alternating current generated by electric machine120 to direct current for storage at the electric energy storage device132 and vice versa. A second inverter system controller (ISC2) 147 mayconvert alternating current generated by electric machine 135 to directcurrent for storage at the electric energy storage device 132 and viceversa. Electric energy storage device 132 may be a battery, capacitor,inductor, or other electric energy storage device. Electric energystorage device 132 may be insulated from vibrations in the vehiclechassis via mounts 129 that include piezoelectric devices 128.Similarly, the vehicle's chassis may be insulated from suspensionvibrations via mounts 129 that include piezoelectric devices 128. Notethat the chassis mounts may be different from the electric energystorage device mounts.

In some examples, electric energy storage device 132 may be configuredto store electrical energy that may be supplied to other electricalloads residing on-board the vehicle (other than the motor), includingcabin heating and air conditioning, engine starting, headlights, cabinaudio and video systems, etc.

Control system 14 may communicate with one or more of electric machine120, energy storage device 132, electric machine 135, etc. Controlsystem 14 may receive sensory feedback information from one or more ofelectric machine 135, electric machine 120, energy storage device 132,etc. Further, control system 14 may send control signals to one or moreof electric machine 135, electric machine 120, energy storage device132, etc., responsive to this sensory feedback. Control system 14 mayreceive an indication of an operator requested output of the vehiclepropulsion system from a human operator 102, or an autonomouscontroller. For example, control system 14 may receive sensory feedbackfrom pedal position sensor 194 which communicates with pedal 192. Pedal192 may refer schematically to a propulsive effort pedal. Similarly,control system 14 may receive an indication of an operator requestedvehicle braking via a human operator 102, or an autonomous controller.For example, control system 14 may receive sensory feedback from pedalposition sensor 157 which communicates with brake pedal 156.

Energy storage device 132 may periodically receive electrical energyfrom a power source 180 (e.g., a stationary power grid) residingexternal to the vehicle (e.g., not part of the vehicle) as indicated byarrow 184. As a non-limiting example, vehicle propulsion system 100 maybe configured as a plug-in electric vehicle, whereby electrical energymay be supplied to energy storage device 132 from power source 180 viaan electrical energy transmission cable 182. During a rechargingoperation of energy storage device 132 from power source 180, electricaltransmission cable 182 may electrically couple energy storage device 132and power source 180. In some examples, power source 180 may beconnected at inlet port 150. Furthermore, in some examples, a chargestatus indicator 151 may display a charge status of energy storagedevice 132.

In some examples, electrical energy from power source 180 may bereceived by charger 152. For example, charger 152 may convertalternating current from power source 180 to direct current (DC), forstorage at energy storage device 132.

While the vehicle propulsion system is operated to propel the vehicle,electrical transmission cable 182 may be disconnected between powersource 180 and energy storage device 132. Control system 14 may identifyand/or control the amount of electrical energy stored at the energystorage device, which may be referred to as the state of charge (SOC).

In other examples, electrical transmission cable 182 may be omitted,where electrical energy may be received wirelessly at energy storagedevice 132 from power source 180. For example, energy storage device 132may receive electrical energy from power source 180 via one or more ofelectromagnetic induction, radio waves, and electromagnetic resonance.As such, it should be appreciated that any suitable approach may be usedfor recharging energy storage device 132 from a power source that doesnot comprise part of the vehicle. In this way, electric machine 120 andelectric machine 135 may propel the vehicle by utilizing a stationaryelectric power source.

Electric energy storage device 132 includes an electric energy storagedevice controller 139. Electric energy storage device controller 139 mayprovide charge balancing between energy storage element (e.g., batterycells) and communication with other vehicle controllers (e.g.,controller 12).

Vehicle propulsion system 100 may also include an ambienttemperature/humidity sensor 198. Vehicle system 100 may also includeinertial sensors 199. Inertial sensors 199 may comprise one or more ofthe following: longitudinal, latitudinal, vertical, yaw, roll, and pitchsensors (e.g., accelerometers). Axes of yaw, pitch, roll, lateralacceleration, and longitudinal acceleration are as indicated. As oneexample, inertial sensors 199 may couple to the vehicle's restraintcontrol module (RCM) (not shown), the RCM comprising a subsystem ofcontrol system 14. In another example, the control system may adjust anactive suspension system 111 responsive to input from inertial sensors199 and piezoelectric devices. The active suspension system may includeadjustable dampeners 117 to actively control suspension dampening.Active suspension system 111 may comprise an active suspension systemhaving hydraulic, electrical, and/or mechanical devices, as well asactive suspension systems that control the vehicle height on anindividual corner basis (e.g., four corner independently controlledvehicle heights), on an axle-by-axle basis (e.g., front axle and rearaxle vehicle heights), or a single vehicle height for the entirevehicle. Data from inertial sensor 199 may also be communicated tocontroller 12, or alternatively, sensors 199 may be electrically coupledto controller 12.

One or more tire pressure monitoring sensors (TPMS) may be coupled toone or more tires of wheels in the vehicle. For example, FIG. 1 shows atire pressure sensor 197 coupled to wheel 131 and configured to monitora pressure in a tire of wheel 131. While not explicitly illustrated, itmay be understood that each of the four tires indicated in FIG. 1 mayinclude one or more tire pressure sensor(s) 197. Furthermore, in someexamples, vehicle propulsion system 100 may include a pneumatic controlunit 123. Pneumatic control unit may receive information regarding tirepressure from tire pressure sensor(s) 197, and send said tire pressureinformation to control system 14. Based on said tire pressureinformation, control system 14 may command pneumatic control unit 123 toinflate or deflate tire(s) of the vehicle wheels. While not explicitlyillustrated, it may be understood that pneumatic control unit 123 may beused to inflate or deflate tires associated with any of the four wheelsillustrated in FIG. 1 . For example, responsive to an indication of atire pressure decrease, control system 14 may command pneumatic controlsystem unit 123 to inflate one or more tire(s). Alternatively,responsive to an indication of a tire pressure increase, control system14 may command pneumatic control system unit 123 to deflate tire(s) oneor more tires. In both examples, pneumatic control system unit 123 maybe used to inflate or deflate tires to an optimal tire pressure ratingfor said tires, which may prolong tire life.

One or more wheel speed sensors (WSS) 195 may be coupled to one or morewheels of vehicle propulsion system 100. The wheel speed sensors maydetect rotational speed of each wheel. Such an example of a WSS mayinclude a permanent magnet type of sensor.

Vehicle propulsion system 100 may further include an accelerometer 20.Vehicle propulsion system 100 may further include an inclinometer 21.

Vehicle propulsion system 100 may further include a brake system controlmodule (BSCM) 141. In some examples, BSCM 141 may comprise an anti-lockbraking system, such that wheels (e.g. 130, 131) may maintain tractivecontact with the road surface according to driver inputs while braking,which may thus prevent the wheels from locking up, to prevent skidding.In some examples, BSCM may receive input from wheel speed sensors 195.

Vehicle propulsion system 100 may further include a motor electronicscoolant pump (MECP) 146. MECP 146 may be used to circulate coolant todiffuse heat generated by at least electric machine 120 and electricmachine 135 of vehicle propulsion system 100, and the electronicssystem. MECP may receive electrical power from onboard energy storagedevice 132, as an example.

Controller 12 may comprise a portion of a control system 14. In someexamples, controller 12 may be a single controller of the vehicle.Control system 14 is shown receiving information from a plurality ofsensors 16 (various examples of which are described herein) and sendingcontrol signals to a plurality of actuators 81 (various examples ofwhich are described herein). As one example, sensors 16 may include tirepressure sensor(s) 197, wheel speed sensor(s) 195, piezoelectric devices128, ambient temperature/humidity sensor 198, inertial sensors 199, etc.In some examples, steering angle sensor 175, sensors associated withelectric machine 135 and electric machine 120, etc., may communicateinformation to controller 12, regarding various states of electricmachine operation.

Vehicle propulsion system 100 may also include an on-board navigationsystem 17 (for example, a Global Positioning System) on dashboard 19that an operator of the vehicle may interact with. The navigation system17 may include one or more location sensors for assisting in estimatinga location (e.g., geographical coordinates) of the vehicle. For example,on-board navigation system 17 may receive signals from GPS satellites(not shown), and from the signal identify the geographical location ofthe vehicle. In some examples, the geographical location coordinates maybe communicated to controller 12.

Dashboard 19 may further include a display system 18 configured todisplay information to the vehicle operator. Display system 18 maycomprise, as a non-limiting example, a touchscreen, or human machineinterface (HMI), display which enables the vehicle operator to viewgraphical information as well as input commands. In some examples,display system 18 may be connected wirelessly to the internet (notshown) via controller (e.g. 12). As such, in some examples, the vehicleoperator may communicate via display system 18 with an internet site orsoftware application (app).

Dashboard 19 may further include an operator interface 15 via which thevehicle operator may adjust the operating status of the vehicle.Specifically, the operator interface 15 may be configured to initiateand/or terminate operation of the vehicle driveline (e.g., electricmachine 135 and electric machine 120) based on an operator input.Various examples of the operator ignition interface 15 may includeinterfaces that require a physical apparatus, such as an active key,that may be inserted into the operator ignition interface 15 to startthe electric machines 135 and 120 to turn on the vehicle, or may beremoved to shut down the electric machines 125 and 12 to turn off thevehicle. Other examples may include a passive key that iscommunicatively coupled to the operator ignition interface 15. Thepassive key may be configured as an electronic key fob or a smart keythat does not have to be inserted or removed from the ignition interface15 to operate the vehicle engine 110. Rather, the passive key may needto be located inside or proximate to the vehicle (e.g., within athreshold distance of the vehicle). Still other examples mayadditionally or optionally use a start/stop button that is manuallypressed by the operator to start or shut down the engine 110 and turnthe vehicle on or off. In other examples, a remote engine start may beinitiated remote computing device (not shown), for example a cellulartelephone, or smartphone-based system where a user's cellular telephonesends data to a server and the server communicates with the vehiclecontroller 12 to start the electric machines.

Thus, the system of FIG. 1 provides for a vehicle system, comprising: avibration insulating mount including one or more piezoelectric devices;a first mass coupled to the vibration insulating mount; a second masscoupled to the vibration insulating mount; and a controller includingexecutable instructions stored in non-transitory memory that cause thecontroller to indicate degradation of an electrical connector inresponse to a voltage output of the one or more piezoelectric devices.The vehicle system further comprises additional instructions to adjustoperation of a vehicle to reduce fretting of the electrical connector inresponse to a frequency and magnitude of the voltage output of the oneor more piezoelectric devices. The vehicle system includes whereadjusting operation of the vehicle to reduce fretting includes adjustingdampening of a vehicle suspension. The vehicle system includes whereadjusting operation of the vehicle to reduce fretting includes adjustinga frequency of rotation of a propulsive effort source. The vehiclesystem includes where the first mass is a battery and the second mass isa vehicle chassis or suspension. The vehicle system includes where thefirst mass is a vehicle chassis and the second mass is a vehiclesuspension. The vehicle system further comprises circuitry to interfacethe one or more piezoelectric devices to a battery. The vehicle systemincludes where the battery supplies power to propel a vehicle.

Referring now to FIG. 2 , an example mount with vibration insulation isshown. Mount 129 includes a first flange 204 for coupling to first mass212. First flange 204 may be constructed of a metal, polymer, or othersuitable material. The first mass 212 may be a vehicle chassis, batteryhousing, or other device that is desired to be insulated from vibrationsthat may occur in a vehicle. Piezoelectric devices 128 may bemechanically coupled to first flange 204 to receive vibrational energythat may be transmitted between second mass 214 and first mass 212.

Mount 129 includes a second flange 208 for coupling to second mass 214.The second flange 208 may also be constructed of a metal, polymer, orother suitable material. The second mass 214 may be a vehicle suspensionor other device that is desired to be insulated from vibrations that mayoccur in a vehicle. Piezoelectric devices 128 may be mechanicallycoupled to second flange 214 to receive vibrational energy that may betransmitted between second mass 214 and first mass 212.

Mount 129 may also include a dampener 206 to insulate transfer ofvibrations from the second mass 214 to the first mass 212, orvice-versa. In one example, dampener 206 may be constructed of rubber orother suitable dampening material.

Piezoelectric devices 128 are electrically coupled to electric energystorage device 132. Electric energy storage device 132 may supply powerto propel a vehicle and operate ancillary devices in a vehicle (e.g.,audio system, displays, heater, windshield wipers, etc.). Interfacecircuitry 250 allows piezoelectric devices 128 to be coupled to electricenergy storage device 132. In some examples, interface circuitry 250 mayinclude inductors and switching components that boost voltage output bypiezoelectric devices to supply electric charge to electric energystorage device 132. In examples where electric energy storage device 132is a battery, interface circuitry 250 may allow piezoelectric devices128 to supply electric charge to one row of cells 254 so that boostingoutput of the piezoelectric device may not be necessary. The one row ofcells may be electrically coupled with other cells in series as shown at252 to increase a voltage of electric energy storage device 132.

It should be appreciated that mount 129 is a non-limiting example of amount and that piezoelectric devices may be coupled to a wide range ofmounts to provide insulation from vibrations in a vehicle. In addition,vehicle suspension components (e.g., shock absorbers) may also includepiezoelectric devices to harvest energy in the vehicle's suspension andto provide data for evaluating electrical connections.

Referring now to FIG. 3 , a plot of vibrational energy in a vehiclecomponent versus frequency of the vibrational energy is shown. Thevertical axis represents vibrational energy and the amount ofvibrational energy increases in the direction of the vertical axisarrow. The horizontal axis represents frequency of the vibrationalenergy and the frequency increases from the left side of plot 300 to theright side of plot 300.

Dashed line 302 represents a threshold vibrational energy amount that isnot desired to be exceeded. The level of dashed line 302 may bedetermined via monitoring fretting of electrical connectors anddetermining what vibrational energy levels increase fretting toundesirable levels. Trace 304 represents vibrational energy that may beobserved in a mount for a new vehicle. Trace 306 represents vibrationalenergy that may be observed in the mount after the vehicle has traveleda predetermined distance (e.g., 50,000 kilometers).

It may be observed that the amount of vibrational energy in curve 306exceeds threshold 302 at frequency f1. Therefore, it may be determinedthat vibrations at frequency f1 may lead to degradation of electricalconnections since threshold 302 may be exceeded at frequency f1. Forexample, if a piezoelectric device is outputting a voltage at frequencyf1 and a voltage that indicates energy level 302 is exceeded for longerthan a predetermined amount of time, then it may be judged thatelectrical connections may be degraded.

Referring now to FIG. 4 , a plot that illustrates a relationship betweenan excitation level (e.g., an amount of vibrational energy transmittedbetween components) and a rate of resistance change in an electricalconnector is shown. The vertical axis represents a rate of resistancechange and the rate of resistance change increases in the direction ofthe vertical axis arrow. The horizontal axis represents excitation leveland the excitation level increases in the direction of the horizontalaxis arrow.

Trace 402 represents a relationship between excitation level and rate ofresistance change. Thus, as the excitation level increases beyond athreshold level, the rate of resistance change increases significantly.Therefore, if an excitation level is exceeded, a rate of resistance mayincrease so that an electrical connection may no longer function toallow transfer of electrical signals and power from a first electricaldevice to a second electrical device. As such, it may be desirable to beable to determine vibrational excitation levels that may be delivered toelectrical connections.

Referring now to FIG. 5 , an example vehicle operating sequenceaccording to the method of FIG. 6 is shown. The sequence of FIG. 5 maybe generated via the system of FIG. 1 in cooperation with the method ofFIG. 6 . The plots are aligned in time and occur at a same time. Thevertical lines at t0-t4 indicate times of particular interest in thesequence.

The first plot from the top of FIG. 5 is a plot of a vibrationexcitation level observed at a mount, where the mount is positionedbetween a battery and a vehicle chassis, versus time. The vertical axisrepresents an amount of a vibrational excitation level and thevibrational excitation level increases in the direction of the verticalaxis arrow. The horizontal axis represents time and time increases fromthe left side of the figure to the right side of the figure. Trace 502represents a vibrational excitation level.

The second plot from the top of FIG. 5 is a plot of a piezoelectricdevice output (e.g., power or voltage) versus time. The vertical axisrepresents an amount of piezoelectric device output and the amount ofpiezoelectric output increases in the direction of the vertical axisarrow. The horizontal axis represents time and time increases from theleft side of the figure to the right side of the figure. Trace 504represents output of a piezoelectric device. Horizontal line 550represents a threshold level above which degradation of electricalconnectors may occur.

The third plot from the top of FIG. 5 is a plot of an amount of vehiclesuspension dampening versus time. The vertical axis represents an amountof vehicle suspension dampening and the suspension dampening amountincreases in the direction of the vertical axis arrow. The horizontalaxis represents time and time increases from the left side of the figureto the right side of the figure. Trace 506 represents a suspensiondampening amount.

The fourth plot from the top of FIG. 5 is a plot of an amount ofpropulsion source speed versus time. The vertical axis represents apropulsion source speed and the propulsion source speed increases in thedirection of the vertical axis arrow. The horizontal axis representstime and time increases from the left side of the figure to the rightside of the figure. Trace 508 represents the propulsion source speed.

The fifth plot from the top of FIG. 5 is a plot of a fretting indicationversus time. The vertical axis represents a fretting indication stateand fretting is indicated when trace 510 is near the level of thevertical axis arrow. Fretting is not indicated when trace 510 is nearthe horizontal axis. The horizontal axis represents time and timeincreases from the left side of the figure to the right side of thefigure. Trace 510 represents the fretting state.

At time t0, the excitation level is medium and the piezoelectric deviceoutput is at a medium level. The suspension dampening level is alsomedium and the propulsion source speed is increasing. Fretting is notindicated.

At time t1, the output of the piezoelectric device exceeds threshold 550so it may be determined that electrical connection degradation isoccurring according to output of the piezoelectric device, which maycorrelate to levels of vibration that are observed via the piezoelectricdevice. The output of the piezoelectric device may be indicative of alevel of vibrations that are delivered to a battery or electric energystorage device via the vehicle's suspension, chassis, and mounts.Fretting is indicated and the dampening of the vehicle's suspension isadjusted (e.g., increased) to reduce vibrations that may be imparted toelectrical devices and electrical connections. Fretting may be indicatedvia a human/machine interface of via a display. In addition, a speed ofthe propulsion source may be adjusted via shifting a transmission, forexample. The speed may be adjusted to a lower speed so as to movefrequency content of vibrations that may be due to the propulsionsource, which may help to reduce a magnitude of vibrations that may beimparted to electrical connections. The excitation level is high.

At time t2, the output of the piezoelectric device falls below threshold550 so the indication of fretting is removed. The suspension dampeningcontinues on at a higher level and the propulsion source speed is lessthan the propulsion source speed at time t1. The excitation level islowered.

At time t3, the output of the piezoelectric device exceeds threshold 550for a second time so it may be determined again that electricalconnection degradation is occurring according to output of thepiezoelectric device. Fretting is indicated and the dampening of thevehicle's suspension is increased to reduce vibrations that may beimparted to electrical devices and electrical connections. In addition,a speed of the propulsion source may be adjusted via shifting atransmission, for example. The speed may be adjusted to a lower speed soas to move frequency content of vibrations that may be due to thepropulsion source, which may help to reduce a magnitude of vibrationsthat may be imparted to electrical connections. The excitation level ishigh.

At time t4, the output of the piezoelectric device falls below threshold550 so the indication of fretting is removed again. The suspensiondampening continues on at a higher level and the propulsion source speedis less than the propulsion source speed at time t3. The excitationlevel is lowered.

In this way, output of a piezoelectric device may be monitored for thepurpose of determining the presence or absence of vibrations that maycause degradation of electrical connections. In addition, mitigatingactions, such as adjusting dampening of a vehicle suspension, may betaken to reduce the possibility of causing further degradation ofelectrical connections.

Referring now to FIG. 6 , an example method for harvesting energy in avehicle and predicting degradation of electrical connectors is shown.The method of FIG. 6 may be incorporated into and may cooperate with thesystem of FIG. 1 . Further, at least portions of the method of FIG. 6may be incorporated as executable instructions stored in non-transitorymemory while other portions of the method may be performed via acontroller 12 transforming operating states of devices and actuators inthe physical world. In other examples, the method of FIG. 6 may beperformed via a controller that is included with a mount or in onecontroller of a distributed control system.

At 602, method 600 locates one or more piezoelectric devices on or nearmounts. The mounts may be electric energy storage device mounts, chassismounts, or other mounts. The piezoelectric devices may be located suchthat vibration of a vehicle chassis, suspension, or electric energystorage device compresses and decompresses the piezoelectric devices.Method 600 proceeds to 604.

At 604, method 600 determines states of one or more electricalconnectors. The electrical connectors may connect electrical componentsto allow electrical current and/or voltage to be transferred from oneelectrical device to another electrical device. In one example, method600 may output a voltage or current that is to be transferred via anelectrical connector. If method 600 judges that the voltage or currenthas been transferred via the electrical connector, method 600 may judgethat the electrical connectors are not degraded. On the other hand, ifthe voltage or current has not been transferred as expected, method 600may judge that the electrical connectors may be degraded. Method 600 mayapply a voltage and/or current to an electrical connector via a powersource and a switch or other device to assess the state of the one ormore electrical connectors. Method 600 proceeds to 606.

At 606, method 600 judges whether or not the electrical connectors aredegraded. For example, if the electrical connector does not transfer avoltage or current from a first electrical device to a second electricaldevice, method 600 may judge that the electrical connectors aredegraded. If the electrical connector does transfer the voltage orcurrent, method 600 may judge that the electrical connectors are notdegraded. If method 600 judges that the electrical connectors aredegraded, the answer is yes and method 600 proceeds to 607. Otherwise,the answer is no and method 600 proceeds to 608.

At 607, method 600 indicates that electrical connections are degraded.The degradation may be due to a broken connection or other condition.Method 600 may indicate degradation of electrical connections to avehicle operator via a human/machine interface. Alternatively, theindication may be provided to other vehicle systems so that a conditionof degradation may be known by vehicle controllers. Method 600 proceedsto exit.

At 608, method 600 generates charge by compressing and decompressing thepiezoelectric devices of the vehicle. The piezoelectric devices may becompressed and decompressed via energy being transferred from avehicle's suspension to a chassis or mounts. The charge that isgenerated via the piezoelectric devices may be stored in an electricenergy storage device. Further, the charge that is generated via thepiezoelectric devices may power a vehicle propulsion source (e.g.,motor), displays, windshield wipers, audio/visual devices, andcommunications equipment within the vehicle. In one example, thepiezoelectric devices may be incorporated into mounts as shown in FIG. 2. Method 600 proceeds to 610.

At 610, method 600 monitors output of the piezoelectric devices. In oneexample, method 600 may monitor a frequency and magnitude of an outputvoltage of piezoelectric devices. Frequency content in the outputvoltage of the piezoelectric device may be determined by processing thevoltage via a Fourier transform. Method 600 proceeds to 612.

At 612, method 600 judges if output of the piezoelectric devices exceedsa threshold magnitude or level at predetermined frequencies. In oneexample, method 600 may compare the voltage output of one or morepiezoelectric devices to a predetermined threshold that may beindicative of fretting of electrical connectors. The predeterminedthreshold may be a function of frequency as shown in FIG. 3 . Inaddition, the predetermined threshold level may be determined viasupplying various vibrations to electrical connectors and measuringfretting via resistance between surfaces of the electrical connectors.If method 600 judges that output of the piezoelectric device does notexceed the threshold, the answer is no and method 600 proceeds to exit.Otherwise, the answer is yes and method 600 proceeds to 614.

At 614, method 600 may perform mitigating actions to reduce apossibility of electrical connector degradation. In one example, method600 may adjust a dampening rate of a vehicle's suspension to change afrequency and magnitude of excitation that reaches electrical connectorsof a device. In another example, method 600 may adjust a rotationalspeed of an electrical propulsion device to change a frequency andmagnitude of excitation that reaches electrical connectors of thedevice. For example, method 600 may shift gears of a transmission orgearbox to change an operating frequency of an electrical propulsiondevice. Method 600 proceeds to 616.

At 616, method 600 judges if the threshold mentioned at 612 has beenexceeded for a predetermined amount of time. The predetermined amount oftime may be an amount of time that it is predicted to take to causedegradation of electrical connections via vibrational energy. Time maybe accumulated each time the threshold is exceeded to determine if thethreshold mentioned at 612 has been exceeded for more than thepredetermined amount of time. If method 600 judges that the thresholdhas been exceeded longer than the predetermined amount of time, theanswer is yes and method 600 proceeds to 618. Otherwise, the answer isno and method 600 exits.

At 618, method 600 indicates degradation of one or more electricalconnections. Method 600 may indicate the degradation via a human/machineinterface, an audible alarm, or other known indicating device. Method600 proceeds to exit.

In this way, piezoelectric devices may harvest free energy in a vehicleand convert the free energy into electrical power to propel the vehicle.In addition, output of the piezoelectric devices may be monitored topredict degradation of one or more electrical connectors.

The method of FIG. 6 provides for a vehicle operating method,comprising: generating an electrical output via a piezoelectric device,the piezoelectric device coupled to a mount that insulates a firstvehicle component from a second vehicle component; and indicatingdegradation of an electrical connector in response to the electricaloutput. The method includes where the indication is provided via ahuman/machine interface. The method further comprises performingmitigating actions to reduce the electrical output of the piezoelectricdevice when the electrical output of the piezoelectric device exceeds athreshold at a predetermined frequency. The method includes whereperforming mitigating actions includes adjusting dampening of a vehiclesuspension. The method includes where performing mitigating actionsincludes adjusting a rotational frequency of a device that providespropulsive effort to a vehicle. The method includes where degradation ofthe electrical connector is determined via an amplitude and frequency ofthe electrical output of the piezoelectric device. The method includeswhere the electrical output is a voltage.

The method of FIG. 6 also provides for a vehicle operating method,comprising: supplying electric power from a piezoelectric device that iscoupled to a first mass, the first mass insulated from a second mass;and operating one or more electric devices including a propulsion sourcewith at least a portion of electric power supplied from thepiezoelectric device. The method further comprises indicatingdegradation of an electrical connector associated with the first mass inresponse to an electrical output of the piezoelectric device. The methodincludes where the first mass is a battery and where the second mass isa vehicle suspension or chassis. The method includes where the firstmass is a vehicle chassis and where the second mass is a vehiclesuspension. The method further comprises performing mitigating actionsto reduce an electrical output of the piezoelectric device when theelectrical output of the piezoelectric device exceeds a threshold at apredetermined frequency.

Referring now to FIGS. 7A and 7B, an example electrical connector 700 isshown. In this example, electrical connector 700 is comprised of a leg702 and a pad 704. Electrical energy may be transferred from the leg 702to the pad 704 or vice-versa.

In FIG. 7A, a thin oxide film 706 exists between leg 702 and pad 704.Since the oxide film 706 is thin, the electrical connector 700 maytransfer electrical energy efficiently. The leg may tend to moverelative to the pad 704 as indicated by arrow 710 when vibrationalenergy or excitation is imparted to an electrical device that isconnected to the leg 702 or to the pad 704. Leg 702 and pad 704 maytransfer electrical energy from electrical connector 700 to electricaldevices such as battery cells, integrated circuits, power distributionbusses, and other electrical components.

In FIG. 7B, a thicker oxide film 706 exists between leg 702 and pad 704.Since the oxide film 706 is thicker, the electrical connector 700 maynot transfer electrical energy efficiently. The oxide film 706 maythicken due to movement between leg 702 and pad 704. The method of FIG.6 may predict thickening of oxide film 706 by comparing output of apiezoelectric device to a threshold level where degradation of theelectrical connector may be expected to occur.

Note that the example control and estimation routines included hereincan be used with various vehicle and powertrain configurations. Thecontrol methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware.

Further, portions of the methods may be physical actions taken in thereal world to change a state of a device. The specific routinesdescribed herein may represent one or more of any number of processingstrategies such as event-driven, interrupt-driven, multi-tasking,multi-threading, and the like. As such, various actions, operations,and/or functions illustrated may be performed in the sequenceillustrated, in parallel, or in some cases omitted. Likewise, the orderof processing is not necessarily required to achieve the features andadvantages of the example examples described herein, but is provided forease of illustration and description. One or more of the illustratedactions, operations and/or functions may be repeatedly performeddepending on the particular strategy being used. Further, the describedactions, operations and/or functions may graphically represent code tobe programmed into non-transitory memory of the computer readablestorage medium in the engine control system, where the described actionsare carried out by executing the instructions in a system including thevarious engine hardware components in combination with the electroniccontroller. One or more of the method steps described herein may beomitted if desired.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific examples are notto be considered in a limiting sense, because numerous variations arepossible. For example, the above technology can be applied to inductionelectric machines and permanent magnet electric machines. The subjectmatter of the present disclosure includes all novel and non-obviouscombinations and sub-combinations of the various systems andconfigurations, and other features, functions, and/or propertiesdisclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

The invention claimed is:
 1. A vehicle operating method, comprising:generating an electrical output via a piezoelectric device, thepiezoelectric device coupled to a mount that insulates a first vehiclecomponent from a second vehicle component; indicating degradation of anelectrical connector in response to the electrical output; andperforming mitigating actions including reducing the electrical outputof the piezoelectric device when the electrical output of thepiezoelectric device exceeds a threshold and adjusting dampening of avehicle suspension.
 2. The method of claim 1, where the indication isprovided via a human/machine interface.
 3. The method of claim 1, whereperforming mitigating actions includes adjusting a rotational frequencyof a device that provides propulsive effort to a vehicle.
 4. The methodof claim 1, where degradation of the electrical connector is determinedvia an amplitude and frequency of the electrical output of thepiezoelectric device.
 5. The method of claim 4, where the electricaloutput is a voltage.
 6. A vehicle system, comprising: a vibrationinsulating mount including one or more piezoelectric devices; a firstmass coupled to the vibration insulating mount; a second mass coupled tothe vibration insulating mount; a controller including executableinstructions stored in non-transitory memory that cause the controllerto: indicate degradation of an electrical connector in response to avoltage output of the one or more piezoelectric devices; and adjustoperation of a vehicle to reduce fretting of the electrical connector inresponse to the voltage output of the one or more piezoelectric devices.7. The vehicle system of claim 6, where adjusting operation of thevehicle to reduce fretting includes adjusting dampening of a vehiclesuspension.
 8. The vehicle system of claim 6, where adjusting operationof the vehicle to reduce fretting includes adjusting a frequency ofrotation of a propulsive effort source.
 9. The vehicle system of claim6, where the first mass is a battery and the second mass is a vehiclechassis or suspension.
 10. The vehicle system of claim 6, where thefirst mass is a vehicle chassis and the second mass is a vehiclesuspension.
 11. The vehicle system of claim 6, further comprisingcircuitry to interface the one or more piezoelectric devices to abattery.
 12. The vehicle system of claim 11, where the battery suppliespower to propel a vehicle.
 13. A vehicle operating method, comprising:supplying electric power from a piezoelectric device that is coupled toa first mass, the first mass insulated from a second mass; operating oneor more electric devices including a propulsion source with at least aportion of electric power supplied from the piezoelectric device; andreducing the electrical output of the piezoelectric device and adjustingdampening of a suspension when the electrical output of thepiezoelectric device exceeds a threshold.
 14. The method of claim 13,further comprising indicating degradation of an electrical connectorassociated with the first mass in response to an electrical output ofthe piezoelectric device.
 15. The method of claim 14, where the firstmass is a battery and where the second mass is a vehicle suspension orchassis.
 16. The method of claim 13, where the first mass is a vehiclechassis and where the second mass is a vehicle suspension.